1. Field of the Invention
This invention relates to a tape cartridge in general, and, more particularly, it is concerned with a tape guide for guiding a magnetic tape during its running in a magnetic tape cartridge for VTR.
2. Description of the Prior Art
Conventionally, the magnetic tape cartridge is made up in such a manner that an upper half case and a lower half case, each being formed of a plastic material, are put together, then a tape feeding reel and take-up reel are fitted in an internal space defined by the upper and lower half cases, and the magnetic tape is loaded on and extended between the two reels. Further, a plurality of tape guides are provided in the magnetic tape cartridge to guide the magnetic tape to cause it to pass through a predetermined path, and to stabilize running of the magnetic tape so as to make it possible to record and reproduce informations to a degree of satisfaction.
FIGS. 1 and 2 of the accompanying drawing illustrate, to a good understanding of readers of this specification, one embodiment of the internal structure of the conventional magnetic tape cartridge for VTR, with the upper half case of the magnetic tape cartridge 1 being removed. As exemplified in this embodiment, the magnetic tape T is fed from a tape feeding reel 4 to a take-up reel 6, both being disposed in the lower half case 2. In this instance, the magnetic tape T is guided from the tape feeding reel 4 to a front working part of the cartridge by tape guides 14, 12 and 10, and then further guided to the take-up reel 6 through a tape guide 8 to be taken up on the reel. In the embodiment of the magnetic tape cartridge shown in FIGS. 1 and 2, the tape guides 10 and 12 are fitted on and fixed to shafts 10a and 12a formed at predetermined positions in the lower half case 2 as an integral part thereof, and the tape guide 8 is made freely rotatable on a shaft 8a. Also, the tape guide 14 is a guide pole implanted in a hole 14a formed in one part of the lower half case 2. However, it should be borne in mind that the number, embedding position and structure of the tape guide to be disposed in the magnetic tape cartridge are not limited to the illustrated embodiment, but various modifications may be contemplated to secure stable running of the tape T.
So far, attempts have been made as to constructing this kind of tape guide with metal so as to lower the friction between the tape and the tape guide during running of the tape to prevent the same from getting damaged due to its contact with the tape guide, and to further make smooth the running and guiding of the tape, thereby reducing or perfectly solving the problem to occur during running of the tape. Further, from the standpoint of its use, the tape guide has to be kept away from magnetization, for the reason of which it is generally made of a non-magnetic stainless steel. As is clear from the foregoing statement, it is highly important that the tape guide have a flat and smooth surface, hence the finishing work of its surface to be in contact with the tape is of particular importance.
However, the tape guide made of the conventional nonmagnetic stainless steel material had such disadvantages that not only the material itself was of a high price, but also its productivity was low and its manufacturing cost became high because of poor cutting property stainless steel material possesses in general and necessity for the surface finishing work. Such metal tape guide is further liable to be scratched on its finished surface during a period after its finishing work and before its assemblage in the cartridge, so that very careful handling of the tape guide is needed during this period from its manufacture to its assemblage into the tape cartridge. This has been one of the causes for low productivity in the magnetic tape cartridge to be manufactured in a great quantity.
It has been proposed that the tape guide be formed of a synthetic resin with a view to solving the abovementioned defect which the metal tape guide posseses, but the proposal cannot be totally satisfactory. That is to say, the resin-made tape guide had a serious shortcoming such that the magnetic tape of the synthetic resin is in close contact with the smooth surface of the tape guide to considerably increase the friction between it and the running tape with the consequence that it becomes difficult to achieve the stable running of the tape. Also, dust taken away from the tape due to its frictional contact with the tape guide sticks to the surface of the magnetic tape to be a cause for drop-out of the tape.
In order to solve the defect which the conventional tape guide possesses, the present inventor has proposed the tape guide for the magnetic tape cartridge, which is made of a synthetic resin material and which has a multitude of finely depressed and elevated continuous rectangular portions on the outer surface thereof. This tape guide makes it possible to remarkably reduce the contact surface with the magnetic tape, thereby reducing the friction of the running tape with the tape guide, and to secure stable running of the tape, hence the tape guide has such an effect that no finishing work of the tape contact surface is required even at the time of its manufacture, and is highly suitable for a mass-production.
However, it has been found out that this tape guide of the synthetic resin had a problem in respect of its durability, particularly, sticking of wear-out dust to the tape surface, and the tape guide is charged with static electricity due to friction between the tape guide and the magnetic tape to attract dust floating in the surrounding atmosphere, giving bad effect to the magnetic tape.